Amyl Xyloside, a Selective Sugar-Based Hydrotrope for the Aqueous Extraction of Carnosic Acid from Rosemary

Rosemary ( Rosmarinus officinalis L.) is a Mediterranean herb known for its high antioxidant power that has been widely attributed to carnosic acid (CA). Passive extractions of CA have been performed in water by using five commercially available short-chain alkyl polyglycosides (APG) with alkyl chain lengths ranging from 4 to 10 carbon atoms and polar heads composed of pentoses and/or glucoses. APGs are nontoxic amphiphiles with high biodegradability. Their solubilizing capacity for CA has been determined, highlighting heptyl glucoside (C 7 Glu) as the most efficient one, followed by 2-ethylhexyl glucoside (C 6,–2 Glu) and isoamyl xyloside ( i C 5 Xyl). However, i C 5 Xyl exhibited the highest selectivity toward CA solubilization as compared to ursolic acid (UA), a potential coextracted compound of rosemary leaves. In addition, it was found to be the most efficient amphiphile to extract CA from both ground and whole rosemary leaves. To optimize the maceration process and the recovery of the extract, a full factorial design 2 4 was performed investigating i C 5 Xyl concentration, temperature, stirring, and extraction time. A high concentration of hydrotrope was found to be the most important condition to optimize the maceration step, while the temperature particularly increases the yield, but in detriment of the CA content in the final dried extract.